This invention relates generally to synchronizers for gear transmissions and more particularly to one-way strut type blocking synchronizers.
Strut type blocking synchronizers are well known. See for instance SAE paper 68008 entitled Manual Transmission Synchronizers authored by Richard J. Socin and L. Kirk Walters.
These well known synchronizers employ a plurality of circumferentially spaced struts that key a blocker ring to a guide hub and provide the initial load for indexing the blocker ring so that a shift sleeve can apply pressure to engage a cone clutch. The struts are slidably mounted on the guide hub and operatively connected to the shift sleeve (that ultimately accomplishes the gear lock-up) by spring biased detents that release when forces applied to the struts reach a predetermined limit.
Synchronizers are often used as two-way synchronizers that are located between two unlocked gears on a power shaft. The synchronizer then locks up one gear when the shift sleeve is shifted in one direction and the other gear when the shift sleeve is shifted in the opposite direction. In such situations, the struts for the synchronizer are trapped between separate blocker rings for each of the unlocked gears as shown in FIG. 4 of the SAE publication that is referenced above. Consequently, two way synchronizers do not need any retainers or other structure to limit travel of the struts.
Synchronizers are also used as one-way synchronizers that have only one blocker ring which means that the struts are not trapped. Thus there is a need to limit the travel of the struts in one-way synchronizers in one direction. In the past one-way synchronizers have added either snap rings or sheet metal retainers and snap rings to provide the necessary travel limit in the direction away from the blocker ring.
Both retention methods, however, are relatively expensive. Each involve the manufacture, handling and assembly of an extra part or parts, such as the snap ring alone or in combination with the sheet metal retainer. Each method also involves extra manufacturing steps for securing these extra parts to existing parts, such as machining grooves in the guide hub to hold the sheet metal retainer and/or the snap ring.